Electrical connector



1958 w. H. o. HORNAUER 2,846,649

ELECTRICAL CONNECTOR 2 Sheets-Sheet 1 Filed Sept. 26, 1952 Q'f/mmize A 5, 1958 w. H. o. HORNAUER 2,846,649

ELECTRICAL coumac'roa 2 Sheets-Sheet 2 Filed Sept. 26, 1952 lllllllllllllllllll I iv Z 21 ,JM

United States Patent ELECTRICAL CONNECTOR Willy H. 0. Hornauer, Lemont, Ill., assignor to Ampatco Laboratories Corporation, a corporation of Delaware Application September 26, 1952, Serial No. 311,675

3 Claims. (Cl. 324-155) This invention relates to electrical connectors for a pivotally mounted element and more particularly to electrical connectors for a very sensitive instrument in which a large number of connections must be made to a pivotally mounted element, as in a galvanometer type electromechanical summing amplifier.

A number of difierent types of apparatus have been used for a long time to make electrical connections to rotating or pivoted elements. For example, slip rings and brushes are widely used on motors and generators. In the field of electrical instruments which have pivotally mounted moving elements, it has been common to make electrical connections to the moving element through spiral torsion springs. These springs also returned the instrument coil to its zero position when no current was flowing therethrough. Torsion springs, however, have a number of disadvantages. They are unable, due mainly to temperature'variations, to retain a constant zero position at all times. Furthermore, with two springs it was possibleto make only two electrical connections to the moving element. This raised a serious problem particularly in connection with multi-coil instruments such as mechanical amplifiers in which a number of indivdual coils make up the moving element. A multi-coil instrument has been in use for some time which utilizes an electromagnetic restoring means, thus doing away with the necessity of using torsion springs. The electrical connections were made to the moving element through the number of very thin flexible wires. This greatly reduced the variation of the zero position of the element, but it has been impossible to arrange the wires so as to completely eliminate the torsional action.

Another difiiculty in such instruments results from friction present in the system, mainly in the bearings supporting the movable element. If no friction were present, an input current, however small, would cause a movement of the coil. However, since there is friction present, the input current must exceed a minimum threshold value to cause a response. In a sensitive device it is important that the friction, and consequently the threshold current, be kept as small as possible.

It is an object of this invention to alleviate the above described problems. It is another object to provide connecting means for a pivotally mounted element which has very little or no inherent torsional effect upon the system. A further object is to provide such electrical connectors which minimize the friction in the system. And another object is to provide an electrical connector including an elongated member carried by the pivoted element transversely of the pivotal axis and another elongated member in fixed position relative to the pivoted element and in contact with the first member at a point on the pivotal axis. Anda further object is to provide such a connector in which one of the members has a rounded surface at the point of contact. Yet another object is to provide such a connector in which the contacting surfaces of the members are plated with a precious metal to reduce friction. Yet a further object is to ICC provide such a connector in which the elongated member carried by the pivoted element is normal to and symmetrical with the pivotal axis. Still another object is to pro vide a moving element device having a plurality of aligned connectors. Still a further object is to reduce the friction in the bearings of the moving element of such a device by making at least some of the connectors of a springy material so as to bias the pivoted element upwardly. And another object is to provide such connectors in which the stationary elements are disposed in two aligned groups on opposite sides of the moving element.

Further objects and advantages will become readily apparent from the specification and from the drawings in which:

Figure 1 is a perspective view of a moving coil instrument embodying my invention;

Figure 2 is a top plan view of the instrument of Figure 1;

Figure 3 is a schematic diagram of a summing amplifier which may utilize my invention;

Figure 4 is an enlarged vertical section of a portion of the connector assembly, showing details of the assembly of the elongated members;

Figure 5 is an enlarged verticalsection of a portion of a connector with plated surfaces at the point of contact; and

Figure 6 is a side elevation of a modified connector assembly.

In the embodiment of my invention shown in Figures 1 and 2, a moving coil instrument of a type suitable for use as an electromechanical summing amplifier has a rectangular coil frame 10 comprising the side members and 10b, top 100 and bottom 10d mounted for pivotal movement about the axis of the shaft 11. A thrust bearing 12 supports the lower end 11a of the shaft 11, while bearing 13 provides the proper alignment of the upper end 11b. These bearings are, of course, mounted in an external framework or casing which is not shown in order to simplify the drawings. The bearings 12 and 13 are shown diagrammatically here, .but are preferably some form of jeweled bearing. The elements are preferably so arranged that the pivotal axis is substantially vertical.

The coil frame 10 is adapted for pivotal movement in a magnetic field provided by the cylindrical permanent magnet 14 which has a north pole 15 and a south pole 16. A hollow iron cylinder 17 surrounds the magnet 14 and is supported by the spacing members 18. The magnetic flux leaves the north pole 15 of the magnet, passes through the cylinder 17 and returns to the south pole 16 as indicated by the arrows 19 in Figure 2. This arrangement is preferred rather than the more common horseshoe magnet as it is more compact and has very little magnetic leakage.

Two coils 20 and 21 are wound about the coil frame 10; a current passing through one or both of these coils will react with the magnetic field creating a torque which will tend to turn the coils and the frame assembly about the pivotal axis. More than two coils may be used if desired; for example an electromechanical summing amplifier might have 5 or 6, depending on the number of input signals to be used. It may also be desirable to omit the coil frame 10 and form the coils in a self-supporting structure, as is well known.

A pair of studs 22 and 23 are mounted on the bottom 10d of the frame and extend downwardly therefrom, substantially parallel to and equally spaced from the pivotal axis. If a coil frame is not used, the studs may be mounted on a pair of metal bands encircling the bottom of the coil. A plurality of elongated members or strips 24a, 24b and 240 of electrical conductive material are carried in aligned, spaced relationship by the studs 22 and 23 and each is electrically connected to one side of the coils which make up the moving element, two connectors usually being necessary for each coil. The connections are indicated diagrammatically in Figure l by the leads 25a and 25b from one side of the coils 20 and 21 respectively to the ends of strips 24a and 24b. The other side of each coil is connected to a common strip 24c by the lead 25c. The leads 25 are preferably of a fine wire and may be arranged with parts of them along one of the studs 22 and the rest along the other stud 23 in order to maintain proper balance of the moving element. The strips 24 are preferably of a thin sheet metal such as steel. A sleeve 26 of insulating material surrounds the studs 22 and 23 and insulates the strips 24 therefrom, while sleeves 27 insulate the strips 24 from each other and provide the proper spacing therebetween. A plate 28 is secured to the lower extremities of the studs 22 and 23 and is connected at its midpoint to the lower end 11a of the shaft. The elongated members 24 are preferably normal to and symmetrical with the pivotal axis.

A second plurality of elongated members or strips 29 are mounted in aligned, spaced relationship-on the stud 30 which is mounted in a fixed position with respect to the pivoted assembly. The members 29 are adapted to be connected to external circuits, as by having wires (not shown) soldered to them. Sleeves 31 and 32, of an insulating material, are again provided to properly space and isolate the strips 29. Each of the strips 29 has a free end 29a which is in contact with one of the strips 24; the contact between the pivotally mounted strips 24 and the fixed strips 27 preferably being made along the pivotal axis of the assembly, in order to reduce the frictional torque in the system.

One of each pair of contacting members is preferably provided with a rounded surface at the point of contact, as the cupped depressions 33 in the strips 24. This minimizes the area of contact and reduces the friction appreciably. It is preferable to have the depressions in the strips 24 in order that the points of contact may more readily be positioned along the pivotal axis. It is sometimes desirable to further reduce the friction by plating the contacting surfaces with a layer 34 of precious metal such as gold or silver, as shown in Figure 5.

Some or all of the elongated members 24 and 29 may be made of a springy material, and so arranged that an upwardly directed bias is applied to the pivoted assembly.

Thus, not only are the electrical contacts between the members 24 and 29 made more reliable, but the friction inherent between the thrust bearing 12 and the shaft 11 is reduced.

The summing amplifier shown schematically in Figure 3 is illustrative of the type of instrument with which my connector assembly may be used. Three input coils 36, 37 and 38 and an auxiliary coil 39 make up the coil element wound on the coil frame of Figure l. A pair of resistance elements 40 and'41 are connected in parallel across a source of voltage such as battery 42. The resistance elements 40 and 41 are preferablyresistance wires wound about a form 43, rigidly mounted with respect to the pivoted element. Wipers 44 and 45 are carried by the plate 28 and are in sliding contact with the resistance elements 40 and 41 respectively. The friction between the wipers 44 and 45 and the resistance elements 40 and 41 is kept at a minimum by making the surface of the resistance elements as smooth as possible and using a precious metal such as gold or silver in the wipers.

When no curent fiows through the input coils 36, 37 and 38, the assembly will be in a position such that the wipers 44 and 45 contact points of equal potential on the resistance elements 40 and 41. As a result there will be no output between the terminals 46 and 47. If however signals are applied to one or more of the input coils 36, 37 and 38, a torque will be developed that is proportional to the algebraic sum of the input signals if each of the input coils has the same number of turns. If the coils do not have the same number of turns, the torque will be proportional to the algebraic sum of the products of each input signal multiplied by the number of turns in the input coil to which it is applied.

The auxiliary coil 39 is connected through a variable resistor 48 to the output of the summing amplifier. This coil is so connected that when the signals applied to the input coils cause a torque moving the pivoted element in one direction, the current flowing through the coil 39 causes a torque in the oposite direction. When the signals are removed from the input coils, the current flowing in coil 39 will cause the pivoted element to return to its original position, in which the output is zero. Thus, the coil 39 takes the place of the torsion springs ordinarily used in moving coil instruments and the sensitivity of the movement may be adjusted by the variable resistor 48. The output of the amplifier, present at the terminals 46 and 47 will be directly proportional to the torque produced by the currents flowing in input coils 36, 37 and 38.

The summing amplifier shown schematically in Figure 3 would require 10 connector units: two for each of the three input coils 36, 37 and 38, two for the circuit of the auxiliary coil 39 and two for the output connections to the wipers 44 and 45.

A modification of my invention is shown in Figure 6. Like elements in this figure will be indicated by reference numerals higher than those previously used. The coil frame carries a plurality of spaced, aligned elongated strips 124 as previously described. One portion of the fixed connectors 129 are mounted on a stud 130 while the remainder of the connectors 129 are mounted on a second stud 130. The connectors 129 and 129 are preferably parallel and aligned'diamertically on opposite sides of the pivotal axis of the moving assembly. In this form, the fixed connectors are spaced farther apart and connections thereto may be made more easily.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. Electrical connectors of the character described, comprising: mounting means including a rectangular frame carrying a plurality of coaxially related coil for pivotal movement about a single, transverse, centrally disposed axis, said axis normally being substantially vertical; means for establishing a magnetic flux to be cut by portions of said coils moving circumferentially around said axis; a pair of studs carried by said frame on opposite sides of said axis and extending outwardly from said frame substantially parallel to said axis; a plurality of spaced, parallel, aligned elongated strips of electrical conductive material mounted on said studs to extend therebetween and insulated from each other, said strips extending normal to and symmetrical with said axis and said srips each havinga downwardly extending cupped depression therein, the depressions being aligned along said axis, said strips being operatively connected to said coils; and a plurality of spaced, parallel, aligned elongated strips of electrical conductive springy material fixedly mounted relative to said mounting means, each of said second mentioned strips having a free end in contact with the underside of one of said depressions at a point along said axis, the contacting surfaces of said strips being plated with precious metal, said second mentioned strips being adapted to be electrically connected to an external circuit, for energizing said coils.

2. An electrical connector of the character described, comprising: a coil; mounting means carrying said coil about a transverse pivotal axis; means for establishing a magnetic flux to be cut by a portion of said coil moving circumferentially around said axis; a pair of studs extending from said coil parallel to and on opposite sides of said axis; a first member of conductive material carried between said studs and intersecting said axis, said member being electrically connected to said coil; and a 5 second member of conductive material in fixed position relative to said coil and in electrical conductive contact with said first member at a point on said axis.

3. An electrical connector of the character described in claim 2, wherein arounded portion is struck downwardly from said first member at a point on the extension of the axis of said coil, said second member engaging said surface.

References Cited in the file of this patent UNITED STATES PATENTS Peloux July 19, Evershed Feb. 13, Vawter Oct. 2], Shearer June 18, Colson Apr. 14, Bode Apr. 23,

FOREIGN PATENTS Great Britain June 13, 

